Visual motion processing in the cerebral cortex of the monkey is carried out in a series of specialized areas. We have previously investigated one of these areas, the middle temporal area (MT) and we have now explored the next area, the medial superior temporal area (MST). We investigated the relation of motion processing to the generation of an eye movement that is dependent on such motion processing, smooth pursuit eye movements. We found cells that discharge during pursuit eye movement fell into two groups. Those that were dependent upon visual stimulation lie in the foveal region of MT and lateral MST, while those related to the movement itself were in the lateral and dorsal MST. Punctate removal of cells in these areas of MST using a neurotoxin, ibotenic acid, showed a deficit in pursuit initiation for targets moving in the contralateral visual field (a retinotopic deficit) and a deficit in maintenance of pursuit as long as the target was moving toward the side of the lesion (a directional deficit). We interpret the visual response of cells in MT and the retinotopic deficit as being related to visual stimulation (retinal slip) and the pursuit related cells and the directional deficit as being related to an efference copy signal of pursuit eye movements.